A rotary electric machine such as an electric power generator requires maintenance including inspection of electrical and mechanical soundness using inspection devices. In such an inspection, the inspection device has to access the outer surface of the rotor or the inner surface of the stator. Typically, the rotor is extracted from the stator for inspection, because the gap between the rotor and the stator is narrow when the rotor is inserted in the stator. However, the extraction of the rotor from the stator requires a lot of labor and time.
Meanwhile, inspection technology is being developed where an inspection device is moved in the narrow annular gap between the rotor and the stator while the rotor remains inserted in the stator.